BIOSORPTION OF LEAD (II) ON MODIFIED BARKS EXPLAINED BY THE HARD AND SOFT ACIDS AND BASES (HSAB) THEORY

Chemical modification of Douglas fir bark and its subsequent utilization in adsorption of Pb(II) from aqueous solutions was investigated. The polysaccharidic moiety of barks was functionalized by periodate oxidation and derivatized after reductive amination in the presence of aminated oligo-carrageenans. Pb(II) adsorption isotherms of derivatized barks were then determined and compared to the capabilities of crude barks using the Langmuir adsorption model in terms of affinity (b) and maximum binding capacity (qmax). Compared to crude barks, the derivatization of barks by oligo-carrageenans resulted in significant enhancements of qmax and b by up to x8 and x4, respectively. The results obtained from crude barks on chemically grafted carboxylic and sulfated barks are discussed and interpreted through the Hard and Soft Acids and Bases (HSAB) theory.